Cyanine dyes

ABSTRACT

The present invention relates to chemical substances having dye properties, or more particularly, to improved cyanine dyes and to their application in photographic bleaching processes. Preferably, a chromylium group on the hetero ring comprises either a substituted phenyl group or an alkyl group. More particularly, O-halogenated phenyl and t-butyl groups have proven to be advantageous substituents.

The present invention relates to chemical substances possessingcolouring properties, or, more particularly to cyanine dyes, and relatesfurthermore to the use of such substances in photographic bleachingprocesses.

The substances to which the present invention relates may be expressedby the general formula (I) ##STR1## where:

x₁ or X₂ and Y₁ or Y₂ =oxygen, sulphur, selenium or tellurium, andwhereby each of the remaining X₂ or X₁ and Y₂ or Y₁ (which is not O, S,Se or Te)=Z; Z=CR' or nitrogen; R', R"=a substitutent wherein each R'and R" is chosen from the following groups, independently of the otherR' and R": substituted and unsubstituted hydrogen, includingheterosubstituted alkyl, --cycloalkyl, --aryl, --heteroaryland--alkylaryl; alkoxy, aryloxy, arylalkoxy; carboxylic acid,--ester,--amide and salts thereof; CN; NO₂ ; quaternized nitrogen (NR' havingone or more R'"≠halogen; sulphonic acid and phosphonic acid, includingderivatives and salts thereof; and wherein two R' groups located on thesame ring may bridge together to form a further unsubstituted alicyclicor aromatic ring; n=0 or 1; A=anion.

These substances may be prepared by using known techniques. Thefollowing are listed as examples: O. Riester, Dissertation, Universityof Bonn (1937) for n=0; H. Brockman et al., Ber. dt. Chem. Ges. 77, 529(1944) for n=1.

The heteroatoms (oxygen, sulphur, selenium or tellurium), which areindicated in structure 1 by X₁, X₂, Y₁ and Y₂, may be placed in ringpositions 4 and 4', as has been done for example in the proposedcompounds expressed by structure II and III, ##STR2##

Alternatively, such heteroatoms may also assume ring positions 4 and 2'as in the proposed compound represented by general structure IV.##STR3##

Examples of the proposed compounds are discussed in the followingdisclosure.

It is equally likely for the heteroatoms oxygen, sulphur, selenium andtellurium to take ring positions 2 and 2° or 2 and 4'.

In positions 2, 2', 4 and 4° not occupied by O, S, Se, Te, there ispresent a CR' group or a nitrogen atom.

Although Z in general structure I substantially represents the CR'group, one or more of ring positions 3, 5 and 6 may be replaced by anitrogen atom. These substances, which may also be synthesised by priorart techniques, are suitable for use as bleaching dyes as the followingstructure illustrates: ##STR4## wherein lambda max=548 nm.

It is preferable that one or more of the R" groups in expressions I toIV be hydrogen, however, there also exist stable compounds possessinggood bleaching properties wherein one or more of the R" groups are, forexample, substituted phenyl, t-alkyl, carboxyl, CF₃ or CN. Because ofthe steric requirements placed on mono or trimethylene chains, nosubstituents having large steric requirments may be used as an R" group,particularly if all three carbon atoms in the trimethine chain carry R"groups which are not hydrogen.

In general, it can be assumed that substituents advantageouslyinfluencing dye properties may be formed with every R' and R" group.

Some of the requirements listed in this application, being alreadyknown, have not been claimed as novelty.

Cyanine dyes, as expressed by structure A, have already been describedin "Khimiya Geterotsiklicheskikh Soedinenii" 1983 (3), 304-308. ##STR5##wherein R'₁, R'₂ and R'₃ may each be H at the same time or alternativelyR'₁ or R'₂ or R'₃ =--OCH₃ or R'₁ =--OH. The bleaching properties of suchdyes have not been investigated in this pre-patent document.

Cyanine dyes having chromylium or thiachromylium groups are also listedin various patents obtained by the Eastman Kodak Company. These will bediscussed further in the present disclosure.

Although first suggested in 1900, the production of colour photographsby selectively bleaching individual dyes in a mixture, a deceptivelysimple process, has not achieved any practical significance until thepresent day, despite the early availability of a suitablephotosensitiser in N-allylthiourea, a compound easily removed by water,and capable of facilitating the fixing of a photograph.

The main drawback of this prior art process is that conventional dyesbleached too slowly and left a coloured, mostly yellow-brown residue.

The dyes from the Eastman Kodak Company as disclosed in DE-OS 29 03 287and U.S. Pat. No. 4,247,799 are ill-suited for the production of colourphotographs and/or colour photocopies, since it has been establishedthat the rapid-bleaching dyes leave a dark yellow-brown residue duringthe course of bleaching. Colour reproduction is consequently poor, andin particular, the white areas on the photograph appear to beyellow-brown in colour. An example of a known dye, described in U.S.Pat. No. 4,247,799, is referred to in example 1 as No. III. The negativeimpact of the prior art method upon the bleaching process used in themanufacture of colour filter assemblies for CCD's, is minimal because100% transmission is not required, which lessens the effect of colourresidue deposition. Other dyes are described in U.S. Pat. Nos. 3,300,314and 3,671,251 as well as in JP patent 61-83533 and JP patent applicationNo. 27781/1982.

The objects of the present invention are the creation of new cyaninedyes and identification of a method suitable for preparing such dyesthat reduces the amount of colour residue deposited during thephotographic bleaching process, affords increased light sensitivity andreduces bleaching times.

These deficiencies have been resolved by the cyanine dyes described inthe independent claims.

A precise colour tone may be achieved by use of the proposed dyes. Sincethe photographic bleaching process admits the combination of more thanthree dyes--in contrast to most of the other colour photographyprocesses--the simultaneous employment of the proposed cyanine dyesallows heretofore unattainable true colour reproduction.

The proposed dyes, which are structurally related to the prior art(Thia-)chromylium dyes, distinguish themselves from the latter largelyby increased--in some cases substantially--light sensitivity and, moreparticularly, by their tendency to deposit, following the bleachingprocess, reduced or hardly perceptible amounts of residue. The colourfilm inevitably connected with use of the known dyes is practically nonexistent if the best of the proposed dyes are used; for example, thevalue of E.sub.∞ (450)=0.01 mentioned later in this disclosure signifiesa barely perceptible amount of colour residue.

The proposed dyes are thus suited for use in the preparation of allkinds of colour reproduction, for example colour proofing in printingplate manufacture; assembly of colour filter equipment; monochromecopying in a wide variety of colours and, more particularly, in themanufacture of photographic-quality colour copies. The proposed dyes,when used in the diazo process, eliminate the ever-present, annoyingsmell of ammonia.

The dyes disclosed in the above-noted Eastman Kodak prepublication areexpressed by the general structures II or III, where X₁, Y₁ =oxygen,R'₂, R'₃, R'₆ and R'₇ -R'₁₄ =hydrogen and R"₁ -R"₃ =hydrogen.

In the prior art monomethenylcyanines (n=0), R'₁ and R'₄ (structure III)or R'₁, R'₄ and R'₅ (structure II) are unsubstituted phenyl. Theabove-noted publications disclose a compound possessing two pyryliumgroups as the sole trimethine dye (n=1). These prior art substances arenot being claimed as such.

Without limiting the invention to any one theory in particular, it iscurrently assumed that the steric requirements of substitution on thering are quintessential to the superiority of the proposed dyes.

Where phenyls are substituted on the ring, it is apparently mostadvantageous to use bulky and, if possible, electron withdrawingfunctional groups in one or both of the ortho positions on the phenylring. Certain groups such as, for example, CF₃, can be placed withadvantage in almost any position in the phenyl ring. Alternatively, analkyl, or more particularly, a t-butyl group could be used instead of aphenyl group.

COOH and --COOR groups have also proved very advantageous assubstituents (instead of phenyl and alkyl). The preferred substituentshave also proved advantageous if bonded to a methine group.

Because little is known about the dynamics of the photochemicalbleaching reaction, it is impossible to set forth, with any degree ofcertainty, the effects of the present invention upon discrete parametersof the substitution model. Prior art models in no way anticipate howeverthe degree of advantages attainable by using the present invention.

Various tests aimed at comparing conventional dyes with those proposedwill next be described in detail.

After conventional and proposed dyes were synthesised using suitableconventional techniques, their absorption maxima (lambda max) weremeasured in a dilute solution of 1,2-dichloroethane.

The light sensitivity and the amounts of colour-distorting bleachingresidues were determined by means of the following technique:

100 g cellulose acetate-hydrogen phthalate, 40 g polyethylene glycol,having an average molecular weight of 2000, ca 2 g of the dye being usedand 40 g N-allyl-N'-(hydroethylthiourea were dissoved in 11methylglycol. The resulting solution was spread with a spreading bladeonto a polyester film to a thickness of 0.1 mm. After evaporation of thesolvent, the resulting light sensitive film had a thickness of approx.20 μm. The amount of dye used was selected to give the film an opticalthickness of between 1.8 and 2.2 at the absorption maximum.

The film was then exposed to a 150 Watt halogen lamp through anIR-absorbing filter. The time t, during which the optical thickness atthe absortion maximum decreased from a value of 2,0 to 1,0, wasdetermined. Hence a smaller value of t shown in the following tablesalways indicates a correspondingly higher light sensitivity. The "t"given in the tables is only a relative value and may, therefore,depending on the lighting conditions, indicate seconds or minutes.

After the dye was completely bleached out, the remaining dye, whichcould be bleached out no further, was measured spectrophotometrically,to yield a residual optical thickness reading at a wavelength of 450 nm,which is given in the tables as "E.sub.∞ (450)", a value that can beused as a benchmark for the thickness of the yellow colour followingcomplete photochemical degradation of a dye; optimally, E.sub.∞ (450)=0,where no yellow colour remains.

Firstly, the samples in Table 1 from number 1 to 28, were reviewed.Sample 1 is a prior art Eastman Kodak dye as expressed by the generalstructure III, wherein X₁ and Y₁ =oxygen, R'₁ and R'₄ =unsubstitutedphenyl, and where all other R' and all R"=hydrogen.

Samples 2 to 28 are also expressed by the general structure (III),wherein X₁, Y₁ =oxygen; R'₁, R'₄ =phenyl, all other R' and allR"=hydrogen and n=0. As is apparent from Table 1, various substitutionson the phenyl group R'₁ were tested and partly combined with similarsubstitutions on the phenyl group R'₄.

                                      TABLE 1                                     __________________________________________________________________________    Substitution          Substitution                                            on R'.sub.1 (= phenyl)                                                                              on R'.sub.4 (= phenyl)                                                                      λmax                                                                         E.sub.∞                       Sample No.                                                                          (o)                                                                              (m) (p)                                                                              (m)                                                                              (o)                                                                              (o)                                                                              (m)                                                                              (p)                                                                             (m)                                                                              (o)                                                                              [nm]                                                                              t (450)                               __________________________________________________________________________    1                                   603 20                                                                              0,05                                2     F                             599 18                                                                              0,04                                3     Cl                            592 17                                                                              0,03                                4        Cl                         601 20                                                                              0,05                                5     Br                            590 15                                                                              0,03                                6     I                             588 15                                                                              0,03                                7     Cl              Cl            582 12                                                                              0,02                                8     Cl                    Cl      595 18                                                                              0,03                                9     Br              Br            582 10                                                                              0,02                                10           Cl                     593 18                                                                              0,04                                11    Cl        Cl                  591 17                                                                              0,03                                12    Cl Cl  Cl                     589 18                                                                              0,03                                13    Cl           Cl               583 14                                                                              0,02                                14    Cl           Cl Cl         Cl 574  7                                                                              0,01                                15    Cl           F                586 16                                                                              0,03                                16    Cl           F  Cl         Cl 576 11                                                                              0,02                                17       CF.sub.3                   597 16                                                                              0,06                                18       CF.sub.3        CF.sub.3   598 12                                                                              0,06                                19       CF.sub.3                                                                             CF.sub.3            594 14                                                                              0,07                                20       CF.sub.3                                                                             CF.sub.3            604 10                                                                              0,05                                21       CN                         601 20                                                                              0,10                                22           CN                     607 25                                                                              0,12                                23    NO.sub.2                      586 13                                                                              0,12                                24       NO.sub.2                   597 20                                                                              0,08                                25    CH.sub.3                      592 15                                                                              0,05                                26    CH.sub.3        Cl         Cl 575 12                                                                              0,04                                27    CH.sub.3                                                                             CH.sub.3                                                                            CH.sub.3         583 21                                                                              0,03                                28    CH.sub.3                                                                             CH.sub.3                                                                            CH.sub.3                                                                         Cl         Cl 570 16                                                                              0,02                                __________________________________________________________________________

Sample No. 14 yielded the best results with practically a threefoldshorter bleaching time and a fivefold reduction in the amount ofresidual yellow tone. In this proposed dye, both phenyl groups R'₁, R'₄were each substituted with chlorine at both ortho positions.

Equally good results were obtained by substitutinq both phenyl groupsR'₁ and R'₄ at one ortho position with bromine (sample N_(o) 9)

Table 1a lists the results from samples numbered 85-96. These samplesare expressed by general structure III wherein n=O, X and Y=oxygen. Asin the case of samples 1 to 28, R'₁ and R'₄ were formed using phenylgroups; in the cases of samples 87 and 88, the phenyl group R'₁ wassubstituted with halogen, whereas both phenyl groups R'₁ and R'₄ wereunsubstitued in samples 85, 86 and 89 to 96. In contrast to samples 1 to28, one or more of the substituents R'₇ to R'₁₄ in samples 85-96, whichwere hydrogen, were replaced by halogen atoms, or, as in the case ofsample 96, by methyl groups.

Sample No. 87, which is comparable to sample No. 5, yielded after thesame bleaching time a correspondingly low amount of residual yellowcolour. Sample No. 88, which is comparable to sample No. 11,demonstrated a somewhat shorter bleaching time with larger amounts ofbleaching residue.

By and large, all samples listed in Table la up to the methylsubstituted sample 96 demonstrated shorter bleaching times compared withthe prior art dye (sample No. 1) while yielding the same amount ofbleaching residue.

Samples 90 to 92, wherein R'₇ =Cl, were too unstable to make adetermination of bleaching time and bleaching residue.

                                      TABLE 1a                                    __________________________________________________________________________        Substitution Further substitution in                                      Sample                                                                            on R'.sub.1 (= Phenyl)                                                                     accordance with structure III                                                                         λmax                          No. (o)                                                                             (m)                                                                              (p)                                                                             (m)                                                                              (o)                                                                              R'.sub.7                                                                         R'.sub.8                                                                         R'.sub.9                                                                         R'.sub.10                                                                        R'.sub.11                                                                        R'.sub.12                                                                        R'.sub.13                                                                        R'.sub.14                                                                        [nm]                                                                              t E.sub.∞  (450)           __________________________________________________________________________    85                  Cl    Cl Cl    Cl    627 10                                                                              0,05                           86                  Cl    Cl             610 10                                                                              0,09                           87  Br              Cl    Cl             593 15                                                                              0,03                           88  Cl     Cl       Cl    Cl             595 15                                                                              0,06                           89                     Cl Cl             607 15                                                                              0,07                           90               Cl Cl                   618                                  instabil -                                                                    91               Cl       Cl             616                                  instabil -                                                                    92               Cl Cl Cl                622                                  instabil -                                                                     93                 Cl                   608 15                                                                              0,06                           94                  Br                   609 13                                                                              0,06                           95                  Br    Br             605 13                                                                              0,08                           96                  CH.sub.3                                                                            CH.sub.3       603 30                                                                              0,05                           __________________________________________________________________________

Table 2 lists the results of additional experiments on samples 29 to 42and 97 to 101, as well as dyes corresponding to the general structureIII wherein X and Y=oxygen. Such dyes differ from samples 1 to 28 byhaving an alkyl group or a carboxylic acid or -ester group as thesubstituent R' rather than the phenyl group; the substituent R'₄ isphenyl, substituted if necessary. R'₈ and R'₁₀ ═Cl in two samples.

Good results were obtained with the t-butyl group as substituent R'₁.Although the bleaching times were somewhat longer, the amount ofresidual yellow colour was considerably lower compared with the priorart dye (Sample 1).

Particularly good results were obtained from samples 99, 100 andespecially 101, wherein R'₁ ═COOH and both ortho positions on the phenylgroup R'₄ were substituted with chlorine.

                                      TABLE 2                                     __________________________________________________________________________                Substitution   Further                                                        on R'.sub.4 (= Phenyl)                                                                       substitution                                                                        λmax                                  Sample No.                                                                          R'.sub.1                                                                            (o)                                                                              (m)                                                                              (p)                                                                              (m)                                                                              (o)                                                                              R'.sub.8                                                                         R'.sub.10                                                                        [nm]                                                                              t E.sub.∞  (450)                   __________________________________________________________________________    29    Methyl                     572 50                                                                              0,08                                   30    Methyl                                                                              Cl          Cl       555 30                                                                              0,05                                   31    i-Propyl                   573 40                                                                              0,06                                   32    i-Propyl                                                                            Cl          Cl       557 25                                                                              0,05                                   33    Cyclohexyl                 575 40                                                                              0,06                                   34    Cyclohexyl                                                                          Cl          Cl       563 25                                                                              0,05                                   35    t-Butyl                    574 30                                                                              0,03                                   36    t-Butyl                                                                             Cl                   565 25                                                                              0,03                                   37    t-Butyl                                                                             Br                   563 25                                                                              0,03                                   38    t-Butyl                                                                             Cl          Cl       557 25                                                                              0,03                                   39    t-Butyl                                                                             Cl          F        562 40                                                                              0,03                                   40    t-Butyl                                                                             CH.sub.3                                                                            CH.sub.3                                                                            CH.sub.3 558 35                                                                              0,03                                   41    l-Adamant.                 577 60                                                                              0,05                                   42    l-Adamant.                                                                          Cl          Cl       559 50                                                                              0,05                                   97    t-Butyl              Cl Cl 579 25                                                                              0,04                                   98    t-Butyl                                                                             Cl          Cl Cl Cl 570 22                                                                              0,03                                   99    COOH                       584 35                                                                              0,02                                   100   COOCH.sub.3                580 30                                                                              0,02                                   101   COOH  Cl          Cl       578 25                                                                              0,01                                   __________________________________________________________________________

An equally, very distinct, attenuation in the bleaching yellow tone isobtained with the dyes given in Table 3; this is especially distinct forR'₁ ═CONH₂, (Compare Sample No. 103).

Samples 43, 102 and 103 correspond to the samples in Table 2, howeverR'₄ is t-butyl instead of phenyl.

                  TABLE 3                                                         ______________________________________                                                                   lambda max                                         Sample No.                                                                            R'.sub.1  R'.sub.4 [nm]     t   E.sub.∞  (450)                  ______________________________________                                         43     t-Butyl   t-Butyl  547      30  0.02                                  102     COOCH.sub.3                                                                             t-Butyl  558      30  0.02                                  103     CONH.sub.2                                                                              t-Butyl  558      25  0.01                                  ______________________________________                                    

Table 4 shows the results that were obtained for samples 44 to 53 and104. These dyes correspond to general structure III wherein n=0 and X₁=oxygen, however, Y₁ =sulphur, R'₁ and R'₄ are phenyl groups. In thecase of samples 44 to 53, all the other R' and R"=hydrogen; in the caseof sample 104, R'₈ and R'₁₀ =Cl, and all other R', R"=H.

Sample 44 is a prior art dye in which the R'₁ and R'₄ are unsubstitutedphenyl.

Each substitution of the phenyl group lead to a decreased bleaching timeand an attenuated yellow tone. Sample 51 yielded the shortest bleachingtime and the lowest amount of remaining yellow tone; again in this dye,both phenyl groups R'₁, R'₄ were substituted by chlorine in both orthopositions.

                                      TABLE 4                                     __________________________________________________________________________    Substitution       Substitution lambda                                        on R'.sub.1 (= phenyl)                                                                           on R'.sub.4 (= phenyl)                                                                     max                                           Sample No.                                                                          (o)                                                                             (m)                                                                              (p)                                                                              (m)                                                                              (o)                                                                             (o)                                                                             (m)                                                                              (p)                                                                              (m)                                                                              (o)                                                                             [nm]                                                                              t E.sub.∞  (450)                    __________________________________________________________________________    44                              652 90                                                                              0,06                                    45    Cl                        639 55                                                                              0,04                                    46    Cl   Cl                   641 65                                                                              0.05                                    47    Br                        638 50                                                                              0,03                                    48    I                         638 50                                                                              0,03                                    49    Cl           Cl           633 20                                                                              0,02                                    50    Cl      Cl   Cl           622 15                                                                              0,02                                    51    Cl      Cl   Cl         Cl                                                                              606 12                                                                              0,02                                    52      CF.sub.3                645 35                                                                              0,05                                    53      CN                      645 40                                                                              0,08                                    104     R'.sub.1, R'.sub.4 = unsubstituiertes Phenyl;                                                         653  50                                                                             0,04                                            R'.sub.8, R'.sub.10 = Cl                                              __________________________________________________________________________     Table 5 likewise gives the results for samples 54 to 56, which correspond     to structure III wherein n=O, X.sub.1 and Y.sub.1 =sulphur, R'.sub.1 and     R'.sub.4 =phenyl, all other R' and R"=H.

                                      TABLE 5                                     __________________________________________________________________________    Substitution       Substitution  lambda                                       on R'.sub.1 (= phenyl)                                                                           on R'.sub.4 (= phenyl)                                                                      max                                          Sample No.                                                                          (o)                                                                              (m)                                                                              (p)                                                                             (m)                                                                              (o)                                                                             (o)                                                                              (m)                                                                              (p)                                                                              (m)                                                                              (o)                                                                             [nm]                                                                              t  E.sub.∞  (450)                  __________________________________________________________________________    54                               699 100                                                                              0.08                                  55    Cl           Cl            684 80 0.03                                  56    Br           Br            683 70 0.03                                  __________________________________________________________________________

Sample 54 is a prior art dye wherein R'₁ and R'₄ =unsubstituted phenyl.Chloro- or bromo substitution at the ortho position of the phenylresidue yields decreased bleaching times and drastically diminishedresidual yellow colour.

Table 5a shows the results obtained for samples 105 and 106. The dyesagain correspond to general structure III wherein n=O and R'₁, R'₄=unsubstituted phenyl. X₁ is sulphur; Y₁ is oxygen. In sample 105, R'₁₀=Cl; in sample 106, R'₁₀ =Br. All the other R' and R" are hydrogen.

                  TABLE 5a                                                        ______________________________________                                                                           E.sub.∞  (450)                       Sample No. R'.sub.10                                                                            lambda max   t   [nm]                                       ______________________________________                                        105        Cl    654           80  0.05                                       106        Br    657           70  0.04                                       ______________________________________                                    

For the purposes of this experiment, the monomethine to trimethinecompounds were omitted.

Table 6 shows the properties of samples 57 to 61 and 107 to 109corresponding to general structure III wherein n=1 and X₁ as well as Y₁=oxygen. R'₁ and R'₄ are phenyl groups, and in the case of sample number57 unsubstituted phenyl. For samples 58 to 61 and 107 to 109, R'₁ andR'₄ are substituted phenyl. For samples 57 to 61, all the other R' andR"=H; for samples 107 to 109 individual substitutents R'₇ to R'₁₄ =CH₃,and all the other R' and R"=H.

                                      TABLE 6                                     __________________________________________________________________________    Sam-                                                                             Substitution                                                                              Substitution                                                                             Further substitution in                             ple                                                                              on R'.sub.1 (= Phenyl)                                                                    on R'.sub.4 (= Phenyl)                                                                   accordance with structure II                                                                          λmax                 No.                                                                              (o) (m)                                                                           (p) (m)                                                                           (o) (o) (m)                                                                           (p) (m)                                                                           (o)                                                                              R'.sub.7                                                                         R'.sub.8                                                                         R'.sub.9                                                                         R'.sub.10                                                                        R'.sub.11                                                                        R'.sub.12                                                                        R'.sub.13                                                                        R'.sub.14                                                                        [nm]                                                                              t  E.sub.∞(450                                                             )                    __________________________________________________________________________    57                                                716 200                                                                              0,08                 58 Br          Br                                 684 30 0,02                 59 Cl      Cl  Cl      Cl                         674  3 0,01                 60 CH.sub.3    CH.sub.3                           691 100                                                                              0,01                 61 CH.sub.3                                                                          CH.sub.3                                                                          CH.sub.3                                                                          CH.sub.3                                                                          CH.sub.3                                                                          CH.sub.3                   672 14 0,01                 107                                                                              Cl      Cl  Cl      Cl CH.sub.3                                                                            CH.sub.3 CH.sub.3                                                                            CH.sub.3                                                                         685 35 0,02                 108                                                                              Cl      Cl  Cl      Cl    CH.sub.3       CH.sub.3                                                                            680 20 0,01                 109                                                                              CH.sub.3                                                                          CH.sub.3                                                                          CH.sub.3                                                                          CH.sub.3                                                                          CH.sub.3                                                                          CH.sub.3                                                                         CH.sub.3                                                                            CH.sub.3 CH.sub.3                                                                            CH.sub.3                                                                         683 90 0,02                 __________________________________________________________________________

Also of general structure III, the dyes corresponding to samples 112 and113 have the following structures: ##STR6##

The dye corresponding to sample 112 has already been disclosed inJapanese Patent Application No. 27781/1982 cited at the beginning of thepresent application. The dye corresponding to sample 113 isdistinguished from this prior art dye by the fact that R"₂ is methylinstead of phenyl.

Sample 112 yielded max=727 nm; t=50 and E.sub.∞ (450)=0.09. Sample No.113 yielded lambda max=730 nm; t was greater than 500 which meant thatE.sub.∞ (450) could not be determined.

The foregoing experiments demonstrate that dyes having R"=phenyl arebetter suited as bleaching dyes than are those wherein R"=alkyl. In viewof the substituent effects demonstrated by the dyes investigated aboveit can be assumed that R"=substituted phenyl especially withorthohalogen substituted phenyl, t-alkyl or carboxyl (-derivative)yields substantially better properties compared to the prior art dyecorresponding to sample 112.

Especially outstanding are the properties of samples 59 and 108 in whichboth phenyl groups R'₁ and R'₄ are chlorinated in both ortho positions.Compared to sample 57 as a reference substance, the bleaching time inthe case of sample 59 is reduced by nearly a factor of 70 and theresidual yellow tone is reduced by about a factor of 8. It isinstructive in this respect to make a comparison with samples 1 and 14listed in Table 1.

Table 7 shows the results for samples 62 to 64, 110 and 111. These dyesagain correspond to structure III wherein n=1 and X₁ as well as Y₁=oxygen. R'₁ and R'₄ in such dyes are not phenyl groups, but ratheralkyl groups. For samples 62 to 64 all the other R' and R"=H; forsamples 110 and 111, individual substituents R'₇ to R'₁₄ are Cl or CH₃while the remaining R' and R"=H. The best result was obtained by usingt-butyl as substituents R'₁ and R'₄ (samples 63 and 110).

                                      TABLE 7                                     __________________________________________________________________________                    Further substitution                                          Sample          in accordance with structure II                                                                       λmax                           No. R'.sub.1                                                                            R'.sub.4                                                                            R'.sub.7                                                                         R'.sub.8                                                                         R'.sub.9                                                                         R'.sub.10                                                                        R'.sub.11                                                                        R'.sub.12                                                                        R'.sub.13                                                                        R'.sub.14                                                                        [nm]                                                                              t  E.sub.∞ (450)            __________________________________________________________________________    62  i-Propyl                                                                            i-Propyl                      662 50 0,01                           63  t-Butyl                                                                             t-Butyl                       663 30 0,01                           64  1-Adamant.                                                                          1-Adamant.                    668 60 0,02                           110 t-Butyl                                                                             t-Butyl  Cl    Cl Cl    CL    682 20 0,01                           111 t-Butyl                                                                             t-Butyl                                                                             CH.sub.3                                                                            CH.sub.3 CH.sub.3                                                                            CH.sub.3                                                                         673 70 0,01                           __________________________________________________________________________

An evaluation of the structures represented by general structureII--without the ring between R'₅ and R'₆ corresponding to structureIII--yielded analogous results.

Table 8 shows the results of experiments conducted on samples 65 to 78and 114 to 129. These dyes correspond to structure II wherein n=O and X₁as well as Y₁ =oxygen. R'₁, R'₄ and R'₅ compare phenyl groups; R'₄ andR'₅ are unsubstituted for all the samples in Table 8. For samples 65 to78, all the other R' and R"═H. For samples 114 to 129, individualsubstituents R'₇ to R'₁₀ ═Cl, Br or CH₃ ; all further R' and all R"═H.

                                      TABLE 8                                     __________________________________________________________________________                     Further substitution                                             Substitution in accordance with                                           Sample                                                                            on R'.sub.1 (= Phenyl)                                                                     structure II                                                                              max                                              No. (o)                                                                              (m)                                                                              (p)                                                                             (m)                                                                              (o)                                                                             R'.sub.7                                                                         R'.sub.8                                                                         R'.sub.9                                                                         R'.sub.10                                                                        [nm]                                                                             t E (450)                                     __________________________________________________________________________     65                          570                                                                              80                                                                              0,20                                         66 Cl                       565                                                                              50                                                                              0,14                                         67    Cl                    570                                                                              80                                                                              0,18                                         68 Br                       562                                                                              30                                                                              0,12                                         69 I                        562                                                                              30                                                                              0,12                                         70 Cl    Cl                 564                                                                              60                                                                              0,16                                         71 Cl      Cl               562                                                                              50                                                                              0,15                                         72 Cl Cl Cl                 559                                                                              50                                                                              0,15                                         73 Cl         Cl            552                                                                              21                                                                              0,14                                         74    CF.sub.3              566                                                                              30                                                                              0,20                                         75    CF.sub.3                                                                           CF.sub.3         563                                                                              30                                                                              0,18                                         76    CN                    568                                                                              40                                                                              0,24                                         77 NO.sub.2                 554                                                                              35                                                                              0,25                                         78 CH.sub.3                 562                                                                              60                                                                              0,11                                        114                 Cl    Cl 574                                                                              50                                                                              0,25                                        115              Cl Cl       576                                              instabil -                                                                    116              Cl    Cl    575                                              instabil -                                                                    117              Cl Cl Cl    582                                              instabil -                                                                    118                       Cl 573                                                                              40                                                                              0,20                                        119                 Cl       575                                                                              30                                                                              0,20                                        120                 Br       577                                                                              25                                                                              0,16                                        121                 CH.sub.3                                                                            CH.sub.3                                                                         577                                                                              80                                                                              0,18                                        122 Br              Cl    Cl 562                                                                              25                                                                              0,15                                        123 Cl              Cl       566                                                                              40                                                                              0,15                                        124 Cl              Br       567                                                                              40                                                                              0,18                                        125 Cl              Br    Br 566                                                                              45                                                                              0,25                                        126 Cl                    Cl 563                                                                              40                                                                              0,15                                        127 Cl      Cl      Cl    Cl 558                                                                              25                                                                              0,15                                        128 Cl         Cl   Br       553                                                                              17                                                                              0,12                                        129 Cl         Cl   Cl    Cl 547                                                                              18                                                                              0,14                                        __________________________________________________________________________

Sample No. 65 is a known dye in which all the phenyl groups areunsubstituted.

Sample No. 128, wherein R'₁ is a phenyl group chlorine substituted atboth ortho positions and with R'₈ =Br, yielded the shortest bleachingtime t. Samples 68, 69 and 78 yielded similarly good results withrespect to the residual yellow colour with longer bleaching times,however. In each case only one ortho position of the R'₁ phenyl groupwas substituted.

With an equally short bleaching time, sample No. 129 yielded practicallythe same low level of bleaching residue, which indicates the favorableeffect of halogenation in R'₈ and R'₁₀ quite apart from the advantageousinfluence of ortho chlorination on the R'₁ phenyl. (Compare with samples122 and 127).

Samples 115 to 117 were unstable, probably because R'₇ =Cl; compare thiswith samples 90 to 92 in Table 1a.

In Table 9 are listed the results for samples 79 to 81 and 130 to 142;these dyes also correspond to general structure II wherein n=O and X₁ aswell as Y₁ =oxygen.

                                      TABLE 9                                     __________________________________________________________________________                       Further substitution                                           Substitution   in accordance with                                         Sample                                                                            on R'.sub.1 (= Phenyl)                                                                       structure II                                                                              λmax                                    No. (o)                                                                              (m)                                                                              (p)                                                                              (m)                                                                              (o)                                                                              R'.sub.7                                                                         R'.sub.8                                                                         R'.sub.9                                                                         R'.sub.10                                                                        [nm]                                                                              t  E∞(450)                           __________________________________________________________________________     79                            536 135                                                                              0,05                                     80 Br                         525 110                                                                              0,04                                     81 Cl          Cl             515  60                                                                              0,03                                    130                   Cl       540  90                                                                              0,05                                    131                         Cl 536 110                                                                              0,09                                    132                Cl Cl    Cl 539 110                                                                              0,07                                    133                Cl    Cl Cl 538 120                                                                              0,08                                    134                Cl Cl Cl    542 125                                                                              0,09                                    135                   Br       540  90                                                                              0,05                                    136                   CH.sub.3                                                                            CH.sub.3                                                                         540 160                                                                              0,05                                    137                   Cl    Cl 538  85                                                                              0,04                                    138 Cl                         527  25                                                                              0,02                                    139 CH.sub.3                                                                            CH.sub.3                                                                            CH.sub.3       520  30                                                                              0,04                                    140 Cl                Cl       530 100                                                                              0,03                                    141 Cl                Br       530 100                                                                              0,03                                    142 Cl                      Cl 527  90                                                                              0,03                                    __________________________________________________________________________     (R'.sub.4,R'.sub.5  = tButyl)                                            

In the case of dye No. 79, R'₁ is unsubstituted phenyl. For dyes 80 and81 an ortho halogen substitution has been made.

For samples 79 to 81 and 130 to 142, R'₄ and R'₅ =t-butyl. For samples79 to 81 and 138, 139 all further R' and R"=H. For samples 130 to 137and 140 to 142 individual substituents R'₇ to R'₁₀ =Cl, Br or CH₃, andall further R' and R"=H.

Especially good results were demonstrated by dye No. 138 wherein R'₁=phenyl monochlorinated in the ortho position and 81 wherein R'₁ =phenylchlorinated in both ortho positions.

It is worth noting, in addition, that dye 139 having phenyl methylatedin both ortho positions as well as in the para-position as substituteR'₁ is not substantially worse. Moreover, it was noted that samples 132to 134 appeared to be quite stable despite R'₇ =Cl.

Table 9a indicates the results for samples 143 to 147. Dyes 143 to 146correspond to structure II wherein n=O, X₁, Y₁ =oxygen, R'₁=unsubstituted phenyl, R'₄ and R'₅ =isopropyl. Sample 143 is thereference substance in which all other R' and R"=H. For samples 144 to146 individual substituents R'₇ to R'₁₀ are Cl, Br or CH₃.

Sample 147 also corresponds to structure II, however R'₁, R'₄ and R'₄=t-butyl. All other R' and R"=H.

                                      TABLE 9a                                    __________________________________________________________________________    Sample                                                                            Substitution with structure                                                                             λmax                                     No. R'.sub.1                                                                          R'.sub.4                                                                           R'.sub.5                                                                           R'.sub.7                                                                         R'.sub.8                                                                         R'.sub.9                                                                         R'.sub.10                                                                        [nm]                                                                              t  E.sub.∞ (450)                      __________________________________________________________________________    143 Phenyl                                                                            i-Propyl                                                                           i-Propyl         534 145                                                                              0,05                                     144 Phenyl                                                                            "    "       Cl       536 120                                                                              0,04                                     145 Phenyl                                                                            "    "       CH.sub.3                                                                            CH.sub.3                                                                         538 160                                                                              0,05                                     146 Phenyl                                                                            "    "       Br       538 110                                                                              0,04                                     147 t-Butyl                                                                           t-Butyl                                                                            t-Butyl          512  90                                                                              0,04                                     __________________________________________________________________________

Finally, experiments were carried out upon dyes corresponding to generalstructure IV, wherein n=O, X₁, Y₂ =oxygen, R'₁ =phenyl (sample 82),substituted phenyl (sample 83) or t-butyl (sample 84); all other R' andR"=H. The results are shown in Table 10.

                  TABLE 10                                                        ______________________________________                                                                     lambda                                           Sample        Substitution on R'.sub.1                                                                     max                                              No.   R'.sub.1                                                                              (o)   (m) (p)  (m) (o) [nm]  t   E.sub.∞ (450)            ______________________________________                                        82    Phenyl                     606   30  0.05                               83    "       Cl             Cl  594   10  0.03                               84    t-Butyl                    582   14  0.03                               ______________________________________                                    

Compared to dye No. 82 which has unsubstituted phenyl as substitutentR'₁, chloro substitution at both ortho positions of the phenyl moleculeyielded a clear improvement (sample 83). The result for sample No. 84having t-butyl as substitutent R'₁ was insignificantly different.

To conclude, the investigations described show that in some cases, theproposed dyes cause an increase in light sensitivity but not animprovement in the yellow tone; in other cases both were obtained. Theintroduction of halogen substituents in the ortho position provedespecially valuable when phenyl groups were introduced into the ring.The replacement of phenyl by t-butyl or carboxyl is likewise especiallyadvantageous. These improvements are more striking in the case of thetrimethenylcyanines than in the case of the monomethenylcyanines.

A film material suitable for use in photographic bleaching processes canbe produced and employed in accordance with the following examples inwhich proposed dyes up to the dye PS can be used.

EXAMPLE 1

In 11 methylglycol were dissolved 100 g cellulose acetate hydrogenphthalate, 40 g polythylene glycol (average molecular weight 2000) and40 g N-allyl-N'-(hydroxyethyl)thiourea as well as 1 gTri(p-methoxyphenyl)pyrylium trifluoroacetate (U.S. Pat. No. 3,300,314).Then 1.2 g of sample 38 dye and 1.8 g of 63 sample dye were added to thestarting solution in the form of trifluoroacetate. The resultingsolution was spread with a blade into a 0.1 mm thick film upon PE-coatedpaper. After evaporation of the solvent, the black-appearing, lightsensitive film had a thickness of approx. 20μm. By means of backlightexposure through a coloured original an orthochromic (positive) copy ofthe original was obtained. Subsequently, the copy was treated with waterand thus rendered light insensitive (fixed).

EXAMPLES 2 TO 7

Additional films were prepared as described in Example 1 in which thefollowing dyes were added to the starting solution; (Sample numbers aregiven as in the description.)

2: 0.9 g No. 40 and 1.8 g No. 58

3: 1.0 g No. 39 and 2.0 g No. 61

4: 1.5 g No. 62 and 1.2 g No. 103

5: 0.5 g No. 35; 0.5 g No. 43 and 1.5 g No. 63

6: 0.6 g No. 26; 0.5 g No. 43 and 1.5 g No. 62

7: 0.5 g No. 35; 1.5 g No. 61; 0.5 g No. 81 and 0.5 g No. 103

All these films yielded colour-true copies.

We claim:
 1. A compound of the formula: ##STR7## wherein (a) R'₁ and R'₄are independently selected from the group consisting of --COOH,--COOCH₃, --CONH₂, tert-C₄ C₂ --C₆ H₅, and --C₆ H₃ Cl₂, with the provisothat either R'₁ or R'₄ is selected from the group consisting of --COOH,--COOCH₃, and --CONH₂ ; and(b) A=anion.
 2. The compound of claim 1wherein R'₁ ═COOH and R'₄ ═--C₆ H₅.
 3. The compound of claim 1 whereinR'₁ ═COOCH₃ and R'₄ ═--C₆ H₅.
 4. The compound of claim 1 wherein R'₁═COOH and R'₄ ═ortho--C₆ H₃ Cl₂.
 5. The compound of claim 1 wherein R'₁═CONH₂ and R'₄ ═tert--C₄ H₉.